Simultaneous transmitting and receiving system with electronic change-over device



y 1943 w. HASENBERG 2,319,680

SIIULTANEOUS TRANSMITTING AND RECEIVING SYSTEM WITH ELECTRONIC CHANGE-OVER DEVICE Filed Jan. 22, 1941 5 Allllll T a smiir neousness of Patented May 18, 1943 UNITED STATES PATENT OFFICE f SIMULTANEOUS TRANSMITTING AND BE- CEIVING SYSTEM WITH ELECTRONIC CHANGE-OVER DEVICE Werner Hasenberg, Rio de Janeiro, Brazil Application January 22, 1941, Serial No. 375,492

In Brazil December 2, 1940 I i 1 Claim. (c1. 179-1) The present invention refers to a system of simultaneous transmission and reception by I means of which the restrictions which are up to now imposed by self-excitation (regeneration) will be. removed.

The best known system of simultaneous transinvention, the characteristics of the telephone.

- are explained below.

Each telephone set consists of a transmitter, represented by the microphone, and a receiver, represented by the earphone. A simultaneous transmission and receiving process requires at least two parties or two telephone sets respectively.

} Due tothe fact that the telephone sets are continuously in condition to either transmitor receive (talk and listen), either party is able to express himself whenever he wants to.

v The telephone system of present design is worka ing on limited energy, and, therefore, the earphone has to be brought near the ear and the microphone near the mouth.

The intercommunicating system is based on working conditions similar to those of the telephone system utilizing nearly the same basic elements. The intercommunicating system also represents a transmitting and receiving system, but not a simultaneous one.v Another diflerence between the telephone and the intercommunicating systems is that the latter has to be operated by means of a talk-listen switch which disconnects the receiving circuit while connecting the transmitting circuit, and vice versa. It is well known that advantages as well as disadvantages result from using this switching device. The advantage consists in the possibility of transmitting and receiving an almost illimited energy-level, whereas the disadvantage is that transmission and reception are consecutive and not simultaneous. Comparing the transmitting.

and receiving operation of the telephone system with that of the intercommunicating system,

it. is noted that the telephone system meanssimultaneous operation whereas the intercommunicating system means consecutive operation. As to energy, it has to be kept'in mind that the telephone system is working on a limited energy level, where as the intercommunicating system allows for applying a high energy level.

The reason for limiting the energy level (telephone system) or desisting from the simultatransmission and. reception by using a talk-listen switch (intercommunicating system) is an electro-acoustical phenomenon called regeneration. No regeneration is observed in the telephone system because of the limited energy level, nor does any possibility of p regeneration exist in the mtercommunicating sysmission and reception is-the telephone system and, for a better understanding of the present tem because of the absence of a closed circuit and because of a talk-listen switch device which changes over to one or the other direction.

The following detailed description. should be A read in conjunction with the accompanying drawing, in which I Fig 1 shows an electric-acoustically closed circuit consisting of two transmitters and two receivers working simulatneously in duplex.

Fig. 2 shows one of the possible circuits according to the invention, demonstrating in what manner the control of the modulator amplifier operates and how it controls a second amplifier connected to the former amplifier.

Fig. 3 complements Fig. 2 showing, diagram-- matically according to the invention, the connection, in duplex operation, of both transmitters and receivers and their mutual control.

Fig. 4 is a graphic representation of the instantaneous values of conductivity or amplification as a function of time during the four phases of the duplex operation.

The above phenomenon of "regeneration is analysed in Figure No. 1, showing a'closed intercommunicating circuit.

The initial energy produced by microphone M| is amplified by transmitter Tl and receiver R-2 and is then received by loudspeaker A-J. A part of this energy emitted by A---! enters microphone M-2 and is then conducted to" transmitter T-! where the energy is again amplified. Receiver R-l receives this energy amplifying it once more and conducting it to its loudspeaker A-l. This electro-acoustical closed circuit becomes self-oscillating entering in regeneration, in case part of the energy emitted by A-i reacts again on M-l.

The present invention which represents a system of simultaneous transmission and reception by means of an electronic changeover device, combines the advantages'oi' the telephone system with those of the intercommunicating system and eliminates their disadvantages, thus makingtransmission and reception possible: (a) simultaneously and (b) with energy theoretically illimited.

The simultaneous transmission and reception systemaccor,ding to this inventionutilizes an automatic control device which reduces amplification of the second party's transmitter at the moment the first party starts to transmit, and vice versa. In other words, the transmitter of the receiving party is automatically decreased to such an extent that it becomes impossible to have i the manifestation retransmitted to the sending party. Due to this system, regeneration is not possible because the entire amplification never reaches a level which would allow such regeneration. The amplification of all units, transmitters and receivers which are connected to the systern, remains during non-operation on an energylevel not sufiicient for exciting the closed circuit to become sell-oscillating (regeneration). Ex-

clusively at the transmitter which is transmitting and only during the time or tn, the

amplification level is higher than the level or nonoperation.

On Figure No. 2 which shows one of the various possible circuits, the manner of operation is explained.

that the rectified voltage at Z is negative, and

' that over R5 it is positive in relation to the ground level of the amplifier, i. e. that the potential. at z and R: will be decreased or increased respectively, proportionate to the modulation produced by the microphone connected at E (Fig. 2). The entire circuit of the transmitting or receiving system has to be completed by the second party's set which is of identical design to that demonstrated on Figure 2 and in this way a circuit is obtained as shown on Figure 3.

Assuming that the total level of amplification oi the entire electro-acoustical c i r, c u i t M'1AaM'.-Ai is aligned in such a manner that the absolute stability is guaranteed in the initial phase (phase of non-operation), i. e., there is no regeneration possible, and one of the parties starts transmitting, the following will happen:

For instance, Ml starting transmission, causes automatically an increase or amplification of its own transmitter (demonstrated by t u b e s Vi-Va--Va) due to decrease of the negative grid polarization of tube V2. high level reception in loudspeaker A: pertaining This will result ina to the second party. Simultaneously-and this is the essentialpoint of this invention-who operating microphonev Mi. 0! the first party will automatically cause decrease of the transmitting level of the secondparty because of the high negative polarization in the grid circuit of tube Vi'. This tube is identical to tube Vi. shown on Figure 2. The polarization from the first party 'to the second party is conducted by line Z-Y'.

when the second party replies to the call received utilizing microphone M: (Fig. 3), the same process will be repeated, as follows: Increase in amplification oi! second party's transmi ter;

Decrease in amplificatioifoi am party'transmitter. Y

During this operation period, the" control is made across line Z'.'-Y.

When the operation or transmitting and receiving between both parties is finished, the ampliilcation of the entire circuit will automatically be reestablished at the initial level according to the nonoperative phase.

On Figure 4 the mutual control is explained with reference to this simultaneous transmission and reception system, in accordance with this invention; furthermore, the shape of the instantaneous levels or amplification or conductivity of both parties during the four phases, is demonstrated.

I. Phase of non-operation.-The amplification in one as well as in the opposite direction of the transmitting and receiving syst'em is established at a level which guarantees the stability or the entire circuit; this means, that the sum of both levels represented by the respective ordinates reaches a previously determined value.

II. Phase oftransmissio n in the direction of M1 to A: (Fig. 3) .-At the moment the amplification increases in the transmitting direction as shown in Figure 4 upper curve, the amplification decreases in the opposite direction (transmitter actually not transmitting), as shown in Figure 4 lower curve.

m. Phase of transmission in the direction of M2 to 41 (Fig. 3) .In this phase of operation, the lower curve belongs to the actually transmitting transmitter and shows a higher level than the curve which belongs to the non-operating transmitter.

IV. Phase of non-operation (Fig. 4).-This phase is identical tophase I.

The conclusion of these explanations is that the transmission and reception system, in acand a loudspeaker and an electronic device selicontained with amplifying means operating as A-type. amplifiers and control means for the mutual control of the gain in either channel so as to reduce the gain in its own channel when a direct current. potential is impressed and produce a rectified direct current P tential when sound energy is transmitted through the channel. both means providing that the overall gain in the two channels is kept below, the level of self-oscillation due to acoustic reed-back in the absence 'and'presence of actual transmission, an outlet for the control potential which is to act I on the opposite channel, and an inlet grounded ioralternating current but receptive for a direct current potentialto be applied from outside. 

